Method of making sublimed litharge



B. 8. WHITE METHOD OF MAKING SUBLIMED LITHARGE Filed Sept. 26, 1954 Nov 9, 11937.

E W. H

W m& T R D m W2 A A Y RB E Patented Nov. 9, 1937 lBflETE-HGD OF MAKING SUBLIMED LITHARGE Bernard Sr White, Hammond, Ind., assignor to The Glidden Company, Cleveland, Ohio, a corporation of Ohio Application September 26, 1934, Serial No. 745,601

2 Claims. (01. 23-146) This invention relates to lead oxide, and has particular reference to a new and novel method of preparing fumed lead oxide (sublimed litharge) whereby unusually high yields of the fumed understood by referring to the accompanying drawing, which is a conventionalized cross-section of the apparatus I prefer to employ, with the burner enlarged out of scale for clarity. A champroduct are obtained. More specifically, it conher (1) is provided, with furnace walls (2). Ex- 5 templates feeding a partially oxidized lead oxide tending into one wall of the furnace is a burner powder directly into a Bunsen flame, thus sub- (3) into which a gas pipe (4) and an air pipe lecting it to the extremely high temperatures (5-) open. Crude litharge is placed in the hopper of the flame, whereby the bulk of the crude (6); it discharges into the mixed air and gas in product is completely oxidized to lead monoxide, the burner, being drawn into the burner partially l0 and is at the same time sublimed into the vapor by suction and partially by gravity. The mixphase. ture of oxide, gas and air discharge through the Heretofore, the common practice in making nozzle (7) and burn in the Bunsen type flame sublimed litharge has been to blow a strong blast (8). The fumed oxide is drawn through a flue of air over molten litharge, whereby the air cur- (9) by the slight draft produced by a fan (10) 15 rent takes up the litharge vapor formed, or, driven by a motor (11); it collects in a dustaIternately, to spray molten lead into a furnace, collector (12). The oxide which is not sublimed, together with some fuel. Both methods are obor which condenses in the furnace, collects as a jectionable, in that the yield of the sublimed p le (13) on the floor of the furnace, from whence product is low, and the resultant residue generit may be raked through a door (14) into con- 20 ally must be reworked to produce a marketable tainers, for use as ordinary li a product. The raw material for the process may be any It has also been proposed to blow a partially partially oxidized lead oxide. Crude green oxidized lead oxide into a furnace, as set out in litharge, obtained by blowing air through pots of my applications, Serial Numbers 692,869 and molten lead while keeping the lead agitated, is 25 692,870. The resultant process is superior to a satisfactory starting product, as is lead subthose commonly practiced heretofore, in that oxide. Powdered lead may beused in the process, considerably higher yields are obtained of fumed but is not preferred, as unless extreme care is product; and, if furnace conditions are kept taken, the residue on the floor oi the furnace may right, the residue is marketable litharge. Howcontain some unoxidized lead. 30 ever, the yield of the fumed product leaves much Furnace temperatures are likewise of considto be desired. If a strong draft is maintained in erable importance. The furnace temperatures the furnace, the yield is somewhat higher, but must be maintained low enough so that the una considerable quantity of unsublimed ordinary sublimed residue will not sinter, so as to require lead oxide is carried over to contaminate the milling; I preferably keep the temperature be- 35 fumed product. Higher yields may also be ob- 10w l,325 F., which is the point at which the tained by increasing furnace temperatures; but residue becomes pasty. The fine temperature if the furnace is hotter than 1,325 E, the resishould, however, be high enough so that there due becomes pasty, and the resultant product will be no red lead in the sublimed oxide. For

cannot be marketed without some after-treatthat reason, flue temperatures should preferably 40 ment. be above the decomposition point of red lead; I

I have discovered that if a crude litharge is prefer to operate at 1,050 E, just above that fed directly into a Bunsen type flame, the lead point. oxide is very largely simultaneously oxidized and The ratio of air to gas should of course be sublimed. A slight draft may be maintained up so regulated as to give complete oxidation of the 45 the flue, to keep the furnace gases moving; and gas and crude raw material, without undue diluthe furnace should be kept at temperatures betion of the gas stream. If it is not desired to low 1,325" R, if it is desired to obtain directly a obtain a directly marketable residue in the furresidue of marketable litharge. The yield of nace, furnace temperatures may be increased to sublimed litharge is very much higher than in increase the yield. The pasty residue may then 50 the case of my old process, approaching when furnace conditions are maintained properly; and the sublimed product is substantially free from ordinary litharge.

The details of my process may be most easily be ground, and reworked; it is a satisfactory raw material for the process. In the event that the process is run in this manner, lead powder may, of course, be used as the raw material.

While the apparatus described shows the preferred form of my invention, other apparatus may be used without departing from the spirit of my invention, the essence of which lies in the simultaneous oxidation and sublimation by the intense heat of a Bunsen flame.

In the claims, sublimed litharge is used to indicate the fumed product, litharge to indicate ordinary lead oxide, and lead-bearing powder to indicate the metal powder, or an oxidized lead raw material.

I claim:

1. The process of making litharge and sublimed litharge, which comprises mixing air, a combustible gas and lead oxide bearing powder before ignition, burning the mixture in a furnace whose lower portion is maintained at or below 1,325 E, collecting litharge on the floor of the furnace, drawing the sublimed litharge through a flue maintained at or above 1,050 F. and separating the sublimed litharge from the flue gases.

2. The method of fractionating a mixture of litharge vapor and litharge dust in a gas stream, comprising forming such a mixture by feeding oxidized lead into an oxidizing flame in a muflle furnace, allowing unvaporized dust to settle and collect in a portion of the combustion chamber adjacent the gas stream while maintaining that portion of the furnace at or below 1,325 F. by regulation of the flame, and drawing the sublimed litharge through a. flue maintained at or above 1,050 F., and separating the sublimed litharge from the flue gases.

BERNARD S. WHITE. 

